Engine cylinder liners are typical components utilized in modern engines, such as internal combustion gasoline engines and diesel engines. An engine cylinder liner includes a bore defined by a longitudinally extended inner surface to accommodate a piston disposed therein. The piston can reciprocate within the bore due to a clearance between an outer surface of the piston and the inner surface of the cylinder liner. A head of the piston and an end of the bore may define a combustion chamber, the volume of which may vary as the piston moves back and forth within the bore. Fuel injected into the combustion chamber is compressed, ignited, and combusted at different engine cycles defined by the movement of the piston.
In many applications, the engine cylinder liners are disposed within an engine block. An engine head assembly is typically disposed on the engine block adjacent one end of the engine cylinder liners. As a result, the engine cylinder liners may be subject to a compression load due to the presence of the engine head assembly. Some portions of an engine cylinder liner may undergo radial deformation under the compression load. The radial deformation of the cylinder liner may distort the otherwise straight profile of the inner surface of the cylinder liner. At some locations, the diameter of the bore may be reduced due to inward deformation of the inner surface of the cylinder liner. The inward deformation of the inner surface may require an increase in the piston ring endgap to avoid piston seizure. However, the increase in the piston ring endgap may reduce the sealing effect and result in an increase in engine oil consumption and contamination, and an increase in the need for breather and filtration capacity in a crankcase ventilation system associated with the engine. Combustion efficiency may also be reduced.
A cast iron cylinder liner is described in U.S. Pat. No. 7,273,029 (the '029 patent) issued to Oda et al. on Sep. 25, 2007. The cast iron cylinder liner includes a plurality of grooves formed on an outer surface of the cylinder liner. Each of the grooves has a ring or spiral shape, extending in a circumferential direction of the cylinder liner. A plurality of such cylinder liners may be placed in a mold, and an aluminum alloy cylinder block may then be cast integrally with the liner. According to the '029 patent, such a cylinder liner design with grooves may reduce residual stress in the cylinder block, thereby preventing the cylinder block from cracking. Also according to the '029 patent, thermal expansion of such a cylinder liner can be controlled to be uniform, which may make it possible to maintain the inner surface in a cylindrical shape and minimize friction caused by a piston reciprocating within the cylinder block.
Although the cylinder liner disclosed in the '029 patent may alter thermal expansion characteristics and help maintain the cylindrical inner surface, reduce engine oil consumption, and reduce abrasion of the piston ring, the cylinder liner may be problematic in some applications. For example, the cylinder liner of the '029 patent may not adequately account for inward radial deformation due to any compressive load that may be applied at a top portion of the cylinder liner, e.g., by an engine head assembly placing a compressive force on the cylinder liner, distorting the shape of the cylindrical inner surface and causing additional abrasion of the piston ring, increased engine oil consumption, and reduced combustion efficiency.
The present disclosure is directed toward improvements in the existing technology.